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# imhmax

H-maxima transform

## Syntax

I2 = imhmax(I,h)
I2 = imhmax(I,h,conn)

## Description

I2 = imhmax(I,h) suppresses all maxima in the intensity image I whose height is less than h, where h is a scalar.

Regional maxima are connected components of pixels with a constant intensity value, and whose external boundary pixels all have a lower value.

By default, imhmax uses 8-connected neighborhoods for 2-D images, and 26-connected neighborhoods for 3-D images. For higher dimensions, imhmax uses conndef(ndims(I),'maximal').

I2 = imhmax(I,h,conn) computes the H-maxima transform, where conn specifies the connectivity. conn can have any of the following scalar values.

Value

Meaning

Two-dimensional connectivities

4

4-connected neighborhood

8

8-connected neighborhood

Three-dimensional connectivities

6

6-connected neighborhood

18

18-connected neighborhood

26

26-connected neighborhood

Connectivity can be defined in a more general way for any dimension by using for conn a 3-by-3-by- ...-by-3 matrix of 0's and 1's. The 1-valued elements define neighborhood locations relative to the center element of conn. Note that conn must be symmetric about its center element.

## Code Generation

imhmax supports the generation of efficient, production-quality C/C++ code from MATLAB. When generating code, the optional third input argument, conn, must be a compile-time constant. Generated code for this function uses a precompiled platform-specific shared library. To see a complete list of toolbox functions that support code generation, see List of Supported Functions with Usage Notes.

## Class Support

I can be of any nonsparse numeric class and any dimension. I2 has the same size and class as I.

## Examples

```a = zeros(10,10);
a(2:4,2:4) = 3;  % maxima 3 higher than surround
a(6:8,6:8) = 8;  % maxima 8 higher than surround
b = imhmax(a,4); % only the maxima higher than 4 survive.```

## References

[1] Soille, P., Morphological Image Analysis: Principles and Applications, Springer-Verlag, 1999, pp. 170-171.